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iridium
8 dictionary results for: Iridium
Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This
i·rid·i·um 
[i-rid-ee-uhm, ahy-rid-] Pronunciation Key
[i-rid-ee-uhm, ahy-rid-] Pronunciation Key –noun Chemistry.
| a precious metallic element resembling platinum: used in platinum alloys and for the points of gold pens. Symbol: Ir; atomic weight: 192.2; atomic number: 77; specific gravity: 22.4 at 20°C. |
Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
American Heritage Dictionary - Cite This Source - Share This
| i·rid·i·um
(ĭ-rĭd'ē-əm) Pronunciation Key
n. Symbol Ir A very hard and brittle, exceptionally corrosion-resistant, whitish-yellow metallic element occurring in platinum ores and used principally to harden platinum and in high-temperature materials, electrical contacts, and wear-resistant bearings. Atomic number 77; atomic weight 192.2; melting point 2,410°C; boiling point 4,130°C; specific gravity 22.42 (at 17°C); valence 3, 4. See Table at element. [From Latin īris, īrid-, rainbow (from the colors produced by dissolving it in hydrochloric acid); see irido- + -ium.] |
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The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Online Etymology Dictionary - Cite This Source - Share This
iridium
iridium
1804, Mod.L., coined by its discoverer, Eng. chemist Smithson Tennant (1761-1815) from Gk. iris (gen. iridos) "rainbow;" so called for the varying color of its compounds.
Online Etymology Dictionary, © 2001 Douglas Harper
WordNet - Cite This Source - Share This
| iridium | |
noun | |
| a heavy brittle metallic element of the platinum group; used in alloys; occurs in natural alloys with platinum or osmium |
WordNet® 3.0, © 2006 by Princeton University.
The American Heritage Science Dictionary - Cite This Source - Share This
| iridium
(ĭ-rĭd'ē-əm) Pronunciation Key
Symbol Ir A rare, whitish-yellow element that is the most corrosion-resistant metal known. It is very dense, hard, and brittle, and is is used to make hard alloys of platinum for jewelry, pen points, and electrical contacts. Atomic number 77; atomic weight 192.2; melting point 2,410°C; boiling point 4,130°C; specific gravity 22.42 (at 17°C); valence 3, 4. See Periodic Table. Our Living Language : In 1978 geologist Walter Alvarez discovered a high concentration of iridium in a layer of clay that had formed between the Mesozoic and Cenozoic eras, a period about 65 million years ago during which dinosaurs and many other organisms became extinct. This finding was significant as iridium is rare at Earth's surface (an unusually high concentration is called an iridium anomaly). Most surface iridium is thought to come from dust created when meteors disintegrate in the atmosphere or collide with Earth. Alvarez's father, the physicist Luis Alvarez, suggested that the iridium might have come from the impact of a meteor about 10 km (6.2 mi) across. Such an impact would have caused an enormous explosion, sending huge clouds of dust into the atmosphere. The dust, blocking out the Sun and causing extensive acid rain, would have triggered a worldwide ecological disaster. Many scientists think that such a disaster caused the extinction of the dinosaurs and at least 70 percent of all other species alive at the time, including most of Earth's land plants. Geologists have since found iridium deposits in rocks of a similar age in more than 100 places worldwide. Scientists in the early 1990s identified a large impact crater in the Yucatán peninsula of central Mexico that is the same age as the iridium deposit found by Alvarez. It is 200 km (125 mi) wide and may have been caused by the same impact. |
The American Heritage® Science Dictionary
Copyright © 2002 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Copyright © 2002 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
American Heritage Stedman's Medical Dictionary - Cite This Source - Share This
iridium i·rid·i·um (ĭ-rĭd'ē-əm)
n.
Symbol Ir
A hard, brittle, corrosion-resistant metallic element. Atomic number 77; atomic weight 192.2; melting point 2,450°C; boiling point 4,430°C; specific gravity 22.42 (at 17°C); valence 3, 4.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Investopedia - Cite This Source - Share This
Iridium
A corrosive resistant element that is sometimes used to harden platinum.
Investopedia Commentary
Iridium is considered to be a precious metal.
See also: Bullion, Palladium, Platinum, Precious Metal, Silver
Investopedia.com. Copyright © 1999-2005 - All rights reserved. Owned and Operated by Investopedia Inc.
Webster's Revised Unabridged Dictionary - Cite This Source - Share This
Iridium
I*rid"i*um\, n. [NL., fr. L. iris, iridis, the rainbow. So called from the iridescence of some of its solutions. See Iris.] (Chem.) A rare metallic element, of the same group as platinum, which it much resembles, being silver-white, but harder, and brittle, and indifferent to most corrosive agents. With the exception of osmium, it is the heaviest substance known, its specific gravity being 22.4. Symbol Ir. Atomic weight 192.5. Note: Iridium usually occurs as a native alloy with osmium (iridosmine or osmiridium), which may occur alone or with platinum. Iridium, as an alloy with platinum, is used in bushing the vents of heavy ordnance. It is also used for the points of gold pens, and in a finely powdered condition (iridium black), for painting porcelain black.
Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
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